1. Field of the Invention
The present invention relates to a cooling duct assembly for a control element drive mechanism, and more particularly, to a cooling duct assembly for a control element drive mechanism (CEDM), in which an upper assembly of a nuclear reactor is conveniently disassembled, moved, and stored by improving structures of a duct which is provided for cooling the CEDM that constitutes the upper assembly of the nuclear reactor.
2. Description of the Related Art
FIG. 1 is a schematic lateral view of an upper assembly of a related nuclear reactor. Referring to FIG. 1, the upper assembly includes a head lift rig 11, a duct, a head area cable tray system (HACTS) 3, and a control element drive mechanism air handling unit (CEDM AHU) 1.
The CEDM AHU 1 circulates cooling air during an operation of a power generator to cool a CEDM 2, and is supported by a shielding wall 4 together with the HACTS 3. The head lift rig 11 is a device for lifting a reactor head 5 for fuel change after stopping the power generator and is installed above the reactor head 5.
The CEDM AHU 1 includes a plurality of cooling fans 6. When the cooling fans 6 operate, surrounding air flows into the CEDM 2. The cooling air flows downwardly between coil assemblies to cool down them, and reaches manifolds 7 after flowing through a nozzle unit of the reactor head 5 and a plurality of holes of a skirt 12.
Afterwards, the cooling air sequentially passes through the manifolds 7 and ducts 8, 9, and 10, and is re-discharged into surrounding flow spaces from the CEDM AHU 1 through the cooling fans 6. There are four manifolds 7, and each manifold 7 includes two branch ducts 8, and thus, eight branch ducts 8 are disposed on the four manifolds 7. The eight branch ducts 8 are combined to four connection ducts 9, and the four connection ducts 9 are combined to two upper ducts 10, and finally, the two upper ducts 10 are connected to the CEDM AHU 1. FIG. 1 shows only a side of the related nuclear reactor, and the nuclear reactor of FIG. 1 has the other symmetrically formed side.
In the upper assembly of the related nuclear reactor, the reactor head 5 needs to be lifted on every fuel change, and at this time, the branch ducts 8, the connection ducts 9, the upper ducts 10, the CEDM AHU 1, and the HACTS 3 must be disassembled and moved to a temporary storage.
More specifically, the CEDM AHU 1 and the HACTS 3 are lifted and moved to a temporary storage. Next, the branch ducts 8, the connection ducts 9, the upper ducts 10, and the manifolds 7 are disassembled, lifted, and moved to a temporary storage separately. The disassembling of the branch ducts 8, the connection ducts 9, the upper ducts 10, and the manifolds 7 requires a lot of time since a plurality of bolts and nuts must be released. Also, the upper region of the related nuclear reactor is a radiation region, and is an elevated place where the branch ducts 8, the connection ducts 9, and the upper ducts 10 are connected, and thus, appropriate measures are needed for workers' safety. Also, when assembling work is performed after refueling is finished, the workload is the same as in the disassembling case and the same safety measures are needed.